High-Frequency LLC Resonant Converter with GaN Devices and Integrated Magnetics

Abstract

In this study, a light emitting diode (LED) driver containing an integrated transformer with adjustable leakage inductance in a high-frequency isolated LLC resonant converter was proposed as an LED lighting power converter. The primary- and secondary-side topological structures were analyzed from the perspectives of component loss and component stress, and a full-bridge structure was selected for both the primary- and secondary-side circuit architecture of the LLC resonant converter. Additionally, to achieve high power density and high efficiency, adjustable leakage inductance was achieved through an additional reluctance length, and the added resonant inductor was replaced with the transformer leakage inductance without increasing the amount of loss caused by the proximity effect. To optimize the transformer, the number of primary- and secondary-side windings that resulted in the lowest core loss and copper loss was selected, and the feasibility of the new core design was verified using ANSYS Maxwell software. Finally, this paper proposes an integrated transformer without any additional resonant inductor in the LLC resonant converter. Transformer loss is optimized by adjusting parameters of the core structure and the winding arrangement. An LLC resonant converter with a 400 V input voltage, 300 V output voltage, 1 kW output power, and 500 kHz switching frequency was created, and a maximum efficiency of 97.03% was achieved. The component with the highest temperature was the transformer winding, which reached 78.6 °C at full load.

Frequency-Dependent Equivalent Circuit Parameter Calculation of Gapped Multiwinding Inductors

“…As a consequence, the field lines lead through the air between the windings (leakage field). 3 Here, γ is the same as defined in section V, (17).…”

“…Gapped multiwinding inductors are essential components in some power electronic converters such as Flyback converters [1] and LLC-converters [2,3]. In multiwinding inductors, the self-and mutual impedances are significantly influenced by the fringing field of the air gap.…”

Equivalent Circuit Element Calculation of Gapped Multiwinding Inductors

“…Gapped multiwinding inductors are essential components in many power electronic converters such as Flyback converters (2) and LLC converters (3) (4) . In multiwinding inductors, the elements of the impedance matrix -i.e.…”

Integrated magnetics optimization process for an interleaved three‐phase buck converter at 500 kHz

“…To simultaneously achieve the goals of high efficiency and high power density, an integrated approach is adopted to reduce the number of required magnetic components. Several methods have been proposed, with the most common ones using integrated non-coupled magnetic components [10] or integrated coupled magnetic components [11][12][13]; the respective concepts are illustrated in Figure 1. Figure 1a shows that the flux loops of the two phases do not affect each other; thus, it is known as an integrated non-coupled magnetic component.…”